Tokyo Olympics held in 1964 were summer games.
Here are links to web sites of official Olympic Movement and Wikipedia:
Until 2000, 10th of October was one of Japan's national holidays as "Taiiku no hi," or Health and Sports Day, to commemorate the opening of the Tokyo Olympic Games. (Since 2000, Health and Sports Day in Japan has been moved to the second Monday in October.)
The first winter Olympic games in Japan was held 1972 in Sapporo, the capital city in Hokkaido Prefecture, and again in 1998, Nagano hosted the winter games for the second time in Japan.